Revised Timber Standards Released - AS 1684 & AS 1720 (Nat)

This information sheet has been prepared to provide HIA members with information about:

• The recent for changes to the Machine Grade Pine (MGP) timber grades under AS 1720.1 – Timber Structures Code; and
• the release of a new 2010 edition of AS 1684 – Residential Timber Framed Construction.

Standards Australia will shortly be publishing a revision of AS 1720.1, the timber structures standard. The new edition has, among other things, changes to the structural design properties of MGP grades of structural timber.

At the same time, a revised 2010 version of AS 1684 has been published which reflects the changes to the MGP properties via revised span tables for MGP grades.

There will be no changes to the span tables for timber F-grades in the revised AS1684 as the design outcomes remain the same under the new version of AS 1720.1.

Both Standards are not referenced under BCA 2010 (released 1 May 2010) but are expected to be referenced under BCA 2011.

Therefore members need to consider the following information when using MGP products between now and the time when the new version of these Standards are referenced by the BCA:

• There will be no BCA requirement for builders to use the revised versions of AS 1720.1 or AS 1684 until such time as they are referenced in the BCA. The anticipated date for adoption is 1 May 2011 through BCA 2011.
• Manufacturers of MGP timber grades have an obligation to produce products that are “fit for purpose”. However they will have no way of controlling or even knowing what version of the standard has been used as the basis of the design or specification for the use of their timber products.
• Unfortunately the structural properties of the MGP grades defined in the old and new standards are not uniformly higher or lower and so direct substitution of one product for the other is not feasible.
• Until the standards are adopted into the BCA, it is feasible that some MGP products will be manufactured to comply with both standards whilst others may be manufactured to either the old or new standard.
• Manufacturers have been asked to advise their customers (our suppliers) as to which method they are employing.
• Therefore when ordering MGP timber products, builders and designers should state which Standard was used in the design process, so that no confusion arises with suppliers as to which grades of timber the order needs to comply with. If there is any doubt, suppliers should be consulted to ensure that their timber will be suitable for the intended purpose.

For further information HIA members can contact HIA’s Building Services staff on 1300 650 620 or hia_technical@hia.com.au

Ref No. NAT BCA 10-19

The above is intended to provide general information in summary form. The contents do not constitute specific advice and should not be relied upon as such. Formal specific advice should be sought by members with respect to particular matters before taking action.  ABN 99 004 631 752